In order to form a desired circuit pattern on a semiconductor device, a lithography technique is used. The lithography technique transfers a pattern using an original pattern, called a mask (reticle). In order to manufacture a high-precision reticle, an electron beam drawing technique having excellent resolution is used.
As one method of an electron beam drawing apparatus which performs an electron beam drawing on a mask, there is a variable-shaped method. In the variable-shaped method, for example, a pattern is drawn on a sample placed on a movable stage by electron beam which is formed by passing through openings of first and second formation apertures and deflection-controlled by a polarizer. One-time irradiation of electron beam is referred to as shot.
During drawing onto the mask or during waiting for drawing, adrift (or beam drift) may occur. That is, an electron beam irradiation position may be deviated from a desired position. For example, when electron beam is irradiated on the mask, reflected electrons are generated. The generated reflected electrons collide against an optical system or a detector within the electron beam drawing apparatus. Therefore, a charge-up is generated and a undesired electric field is generated accordingly. In this case, the trajectory of the electron beam irradiated with deflection toward the mask is changed. As such, the charge-up is one cause of the electron beam drift.
If a drift amount of the electron beam exceeds an allowable range, pattern drawing accuracy is degraded. Therefore, a drift diagnosis for monitoring the drift amount of the electron beam during drawing is performed. As a result of the drift diagnosis, a drift correction is performed to correct the drift according to the obtained drift amount.
JP-A 2010-192666 discloses an electron beam drawing method which changes a time interval of drift correction according to an amount of change in an area density of a region to draw on.